Romeoville, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

053
FXUS63 KDVN 041127
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
627 AM CDT Mon May 4 2026

.KEY MESSAGES...

- Warm temperatures combined with low humidity levels and windy
  conditions will create an elevated fire risk late this morning
  and afternoon. Refer to the fire weather section for more
  information.

- The Storm Prediction Center has a marginal (level 1 out of 5)
  risk for severe storms late this afternoon and evening. Hail
  and damaging winds are the primary risks.

- Northwest flow will result in cooler than normal temperatures
  Tuesday through Friday with a slight warm-up next weekend.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 206 AM CDT Mon May 4 2026

Quiet conditions will be seen through sunrise.

By mid to late morning winds will be on the increase across the area
with gusts up to 30 mph possible through the afternoon. The strong
winds will allow the atmosphere to deeply mix and drop dew points
across the area. The combination of winds, low humidity levels and
warm temperatures will create a marginal fire risk across the area
from late morning through the afternoon in spite of the rapid green
up across the area. Refer to the fire weather section for more
information.

There were many reports yesterday of blowing dust in central and
northern Illinois; generally along/east I-39 and I-55. With wind
speeds forecast to be lower than yesterday, areas of blowing dust do
not appear likely. Spotty blowing dust from farm fields are possible.

With deep mixing dropping dew points during the day, there are
questions regarding convection developing in the afternoon.

All models show the best forcing is along and behind the front
suggesting an anafront. However, closer inspection indicates the
front is not a true anafront nor is it a katafront. It is a hybrid
mix of the two.

The very short term models delay any convective initiation until
late afternoon. This trend is reasonable given the marginal low
level moisture. If the delay trend continues, then convective
initiation looks to occur between 4 and 6 PM and would be isolated
due to the limited moisture.

Once convective initiation occurs, the question is how widespread
will storms become. Based on the 00z extended run of the HRRR,
isolated storms look to be the preferred mode with storms possibly
reaching a 25-35% coverage east of the Mississippi during the
evening.

During the late evening and overnight hours, an upper level
disturbance moves through the area behind the front and the LLJ
increases ahead of the front. This disturbance combined with the
post-frontal forcing and LLJ impinging upon the southward moving
cold front may be enough to generate isolated to scattered (10-35%)
coverage of showers or areas of light rain behind the front.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 206 AM CDT Mon May 4 2026

Tuesday through Wednesday
Assessment...a certainty (>97%) of cooler than normal temperatures.
Low (<20%) confidence on rain.

Northwest flow will result in cooler than normal temperatures across
the area. A surface low that is forecast to move along the cold
front is now taking a further south track. As a result, the model
consensus is keeping areas north of I-80 dry Tuesday through
Wednesday with a 20-60% chance of rain south of I-80. Given the
anomalously low H5 heights over the Great Lakes, a further southward
trend in the rain has a high probability of occurring. I expect the
model consensus to continue lowering rain chances south of I-80 over
the next several model cycles. The ECMWF-AIFS supports this line of
thinking with it indicating Tuesday through Wednesday having a high
probability of being dry.

Thursday through Friday
Assessment...low to medium (20-50%) confidence on daily diurnal
showers

The model consensus continues to have two respectable upper level
disturbances moving through in the flow aloft Thursday and Friday.
However, the model consensus has trended down on the rain chances;
keeping Thursday dry with only 20% chances Thursday night through
Friday evening. Given the limited moisture associated with each
disturbance, the downward trend is reasonable. I still expect some
isolated diurnal showers each day but areal coverage will likely be
10-20 percent at best.

Saturday through Sunday
Assessment...high (>80%) confidence on a slight warm-up

The model consensus agrees that there will be a slight warm-up over
the weekend that will push high temperatures into the lower 70s.

Rain chances are more questionable.

The model consensus has Saturday dry with a system arriving Saturday
night into Sunday. Given differences in track and timing between the
models, rain chances are only at 30 percent.

The overall flow pattern across the CONUS has a ridge along/west of
the west coast with a fairly deep trof along the east coast. All
models show some de-amplification of the pattern occurring by next
weekend. The rain chances boil down the the track of the weekend
system. Based on the flow pattern and the ECMWF-AIFS/AIGFS, the
better rain chances are definitely south of the IA/MO border.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 621 AM CDT Mon May 4 2026

Trends in the HRRR model since the 06z/04 TAF issuance show dew
points dropping indicative of deep mixing. Considerable low
level mechanical turbulence will be seen as winds gust up to 30
knots with slightly lower gusts once the cold front moves
through. The deep mixing raises questions about diurnal
convection developing. HRRR has delayed convection until 22z/04
and is now down to very isolated coverage through 03z/05. A
secondary surge of moisture aloft may initiate isolated to
scattered SHRA after 06z/05.

&&

.FIRE WEATHER...
Issued at 206 AM CDT Mon May 4 2026

Strong daytime heating will result in deep mixing of the
atmosphere late this morning and afternoon. Winds gusting up to
30 mph combined with warm temperatures will drop afternoon
humidity levels into the 25 to 35 percent range. The rapid
green up from the heavier than normal April rainfall will
partially mitigate the fire risk. However, if the deep mixing
causes humidity levels to drop lower than forecast, then the
fire risk would be higher.

Based on the available data, the fire risk from late this
morning through the afternoon is elevated but at the low end of
elevated. Any outdoor burning should still be postponed.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...None.
IL...None.
MO...None.

&&

$$

SHORT TERM...08
LONG TERM...08
AVIATION...08
FIRE WEATHER...08